\usemodule[zhfonts][size=16pt]
\setupzhfonts
  [serif]
  [regular=@1.5, % adjust the scale of default font.
   bold=notoserifcjkscbold@0.5]
  
\starttext
这是汉字，These are English characters.\par
\bf 这是汉字，These are English characters.
\stoptext
